This invention relates to control of the recharging of the battery used to crank a small engine such as is used in a walk-behind lawn mower.
The small gasoline powered piston engine used in walk-behind lawn mowers typically has a power rating in the 3.0 to 4.5 HP range. Most are rope cranked. For those customers desiring a push button starting mode, industry has responded by adding a small DC starting motor to the engine. The starting motor is usually powered by a low capacity 12 volt lead-acid storage battery mounted at an appropriate location on the mower. Cranking by means of the starting motor runs down the battery necessitating the incorporation of a recharging mode. This can be accomplished after the mowing task is completed by coupling a charging unit into a source of 110 volt 60 cps power supplied by the local utility company. Alternatively, a small power generator can be added to the lawn mower engine and the battery recharged during each running thereof, the same as is done with tractors and automobiles.
The engine designers have found a way to incorporate an alternator into the flywheel of the piston engine used in lawn mowing applications. Addition of rectifying diodes in the alternator circuitry produces a pulsating DC output voltage wave train which is useful in charging the lead-acid storage battery. In the prior art systems, the pulsating DC output from the alternator has been coupled directly to the battery without regulation. The result is that the battery tends to be overcharged causing boil-off of electrolyte and shortened life expectancy of the battery.
My invention adds a voltage regulator between the output of the alternator and the storage battery. The voltage regulator prevents overcharging of the battery and greatly improves the useful life thereof.